A typical cellular mobile radio telephone system is controlled by at least one mobile switching center (also known as a mobile telephone switching office), at least one base station, and at least one mobile station. The mobile switching center constitutes an interface between the radio system and the public switching telephone network. The base station transmits information between the mobile stations and the mobile switching center. Calls to and from mobile subscribers are switched by the mobile switching center. The mobile switching center also provides the signalling functions needed to establish the calls.
In order to obtain radio coverage of a geographical area, a number of base stations are normally required. This number may range from, in the exceptional case, one base station, and up to one hundred or more base stations in normal systems. The area is divided into cells, where each cell may either be serviced by a base station or may share a base station with a number of the other cells.
The fast development of cellular telephony has caused the administration of cellular networks and their reconfiguration to become more difficult. Problems with the administration of the networks arise when, for example, the growth of the number of mobile subscribers requires existing cells to be split into several smaller cells or a base station or a mobile switching center becomes temporarily inoperative requiring traffic through that base station or mobile switching center to be temporarily reassigned.
Wire bound telephone networks have had administrative systems for some time. But mobile cellular networks have many parameters and many requirements which are not encountered in the wire bound networks and which are not satisfied by existing administrative systems. For example, the location of the mobile subscribers must be known to the land system in order to direct calls properly. Additionally, each cell has certain associated parameters or characteristics which must be properly maintained to ensure proper operation of the cellular network.
Conventionally, manual or semi-manual ad hoc methods have been used to introduce parameter changes in the cellular networks for reconfiguration purposes and to check the accuracy of the proposed parameter changes. One such manual method used in conventional systems is performed in the following manner. The method will be described with reference to FIGS. 1 and 2 and Table I and using, as an example, a proposed cell split caused by an increase in the number of mobile subscribers. A cell split is described in "CMS 88 Cellular Mobile Telephone System", Ericsson publication EN/LZT 101 908 R2B, Chapter 6 (1987).
FIG. 1 illustrates a simple cell split, which, in this example, consists only of the introduction of one new cell. As shown in FIG. 1, there are five existing cells 1, . . . , 5 (shown in solid lines) and one new cell 6 (shown in dashed lines). Each cell includes a base station BS1, . . . , BS6. There are two mobile switching centers MSC1, MSC2, and cells 1, 5 and 4 are allocated to MSC1, whereas cells 2, 3 and 6 are allocated to MSC2. The cells are connected to their respective mobile switching centers via a PCM link. There is also an administrative center ADM connected to the mobile switching centers MSC1, MSC2 via an X25 link.
FIG. 2 illustrates an example of a manual check which is done in conventional systems when a cell split is being planned and implemented. When the operator at, for example, MSC2 wants to introduce cell 6 in the network, he collects the network parameters involved from MSC2 and MSC1, and prepares the new data required in MSC1 and MSC2, for example, the new neighbor cell definition of FIG. 2. Then he performs a manual check of the proposed changes to determine if any errors have been made. One such check involves determining whether the matrix of FIG. 2 has an equal number of cells in each row and in the corresponding column to ensure that all neighboring cells have been identified properly. This is important since the changes required to introduce a new cell into the network may not only affect the concerned switch, including associated radio base stations and cells, but also the surrounding switches, radio base stations and cells.
If the number of cells in one row is different than the number of cells in the corresponding column, this indicates that there is at least one cell defined as a neighbor for another cell but not visa versa. Other manual and computer assisted checks are also performed before the new data is approved. These manual and semi-manual checks become unduly burdensome and unmanageable as the network grows in size.
Table I illustrates an example of some of the information, i.e., the orders, to be entered into MSC2 to introduce cell 6 in MSC2. A corresponding set of orders is prepared for MSC1. The details of the illustrated commands may be found in the man machine language MML standards (CCITT Yellow Book, Vol. VI, VII Plenary Assembly, Geneva 1981).
In conventional systems, the commands shown in Table I are entered manually by the operator responsible for the mobile switching center concerned. If more than one mobile switching center is involved, the operators agree by telephone what data to enter and when. When installing and starting a complete new network the orders may be provided on a magnetic tape per mobile switching center and entered into the network via tape readers. The manual procedures done conventionally are prone to human error and are very slow. This is of particular concern when reconfiguration is required quickly, with no advance planning possible, due to malfunctions in the network, for example, a failed base station or mobile switching center.
In a cellular network, a large number of parameters and relationships are stored in the mobile switching centers. For operators of these networks, it is difficult to maintain an overview of these parameters and to keep them consistent and correct. It is particularly difficult to maintain consistency when manually implementing a reconfiguration. This difficulty is compounded when several mobile switching centers are operating in the network.
In conventional systems, to survey the cellular network, a copy of all system parameters are maintained in a database, which can be termed the system parameter database. It is important that the system parameter database always contain the current picture of the cellular network. In a rapidly growing network, the system parameter database must therefore be updated frequently and efficiently. This is difficult to accomplish in conventional systems.